The present invention relates to a swim fin with improved angle of attack control and water flow characteristics. More particularly, the present invention relates to a swim fin with a biasing element configured to provide improved angle of attack at various kicking power levels, and to a swim fin with flow channels to provide improved water flow characteristics.
Swim fins are generally known and typically include a foot pocket and a blade portion. A desirable feature of a swim fin is that the blade portion of the fin easily attains a correct xe2x80x9cangle of attackxe2x80x9d during use. The angle of attack is the relative angle that exists between the actual alignment of the oncoming flow (i.e., direction of motion of the swimmer) and the lengthwise alignment of the blade of the fin. A xe2x80x9ccorrectxe2x80x9d angle of attack optimizes the conversion of kicking energy of the swimmer to thrust or propulsion through the water. When this angle is small, the blade is at a low angle of attack. When this angle is high, the blade is at a high angle of attack. As the angle of attack increases, the flow collides with the fins attacking surface at a greater angle. This increases fluid pressure against this surface.
Conventional fins tend to assume different curvatures or attack angles according to the direction of movement and the magnitude of the forces applied during use (i.e., the kicking energy or power). Therefore, it is generally known to design a swim fin to provide a particular angle of attack for a particular kick power. For example, such known swim fins are typically designed for either light kicking, medium kicking, or hard kicking. One way to design a fin for one of these particular kicking powers is by the composition of the material (e.g., stiff material for hard kicking, flexible or soft material for light kicking, etc.). Changing the composition of the material, however, does not efficiently or adequately control the angle of attack, is difficult to match or xe2x80x9csizexe2x80x9d to the strength of the swimmer, and requires the swimmer to use the xe2x80x9cprescribedxe2x80x9d kicking power for that particular fin. Also, most existing fins can only reach a compromise in that they are either stiff, soft, or somewhere in between. When conventional fins are designed for hard kicking (e.g., made of stiff material), they reach the correct angle of attack when kicked very hard. On a normal, relaxed kick they don""t bend far enough and this negatively affects the performance. Fins of this kind will be uncomfortable on the legs, strenuous and with poor performance on a relaxed dive. When conventional fins are designed for light kicking (e.g., made of soft material), they reach the correct angle of attack when kicked very gently. With a strong kick, such as when swimming in a current or needing to get up to speed, the blade is overpowered and there is little or no thrust available. Fins like this might be comfortable on a relaxed dive, but could become unsafe by not being able to provide the thrust to overcome a slight current. When conventional fins are somewhere in between, they can be overpowered when kicked real hard, are still uncomfortable when kicked gently, but cover a wider range of useful kicking power.
When such known fins are used outside their prescribed kicking power, the angle of attach tends to be too low or too high. When the fin blade is at an excessively high or low angles of attack, the flow begins to separate, or detach itself from the low pressure surface of the fin. This tends to cause the fin to be less efficient. Another problem that occurs at higher angles of attack is the formation of vortices along the outer side edges of the fin. This tends to cause drag. Drag becomes greater as the angle of attack is increased. This reduces the ability of the fin to create a significant difference in pressure between its opposing surfaces for a given angle of attack, and therefore decreases the power delivered by the fin.
Accordingly, it would be advantageous to provide a swim fin that provides a desired or optimum angle of attack for a variety or range of kicking strengths or powers. It would further be desirable to provide a swim fin in which the angle of attack is accurately controlled both for the upstroke and for the downstroke so that the ratio of power to fin area is markedly increased (which makes it possible to reduce the overall size of the swim fin without sacrificing total power) for various kicking efforts. It would further be advantageous to control the angle of attack by structural characteristics of bending, not merely by characteristics of materials. It would further be desirable to provide a swim fin with biasing members such as integrally molded, sinusoidally shaped ribs that increase the performance by controlling the angle of attack and converting a higher percentage of the kick energy into thrust. It would further be advantageous to provide a swim fin with flow channels that reduce spillover and provides improved water flow characters. It would further be desirable to provide for a swim fin having one or more of these or other advantageous features.
To provide an inexpensive, reliable, and widely adaptable swim fin with improved angle of attack and water flow characteristics that avoids the above-referenced and other problems would represent a significant advance in the art.
The present invention relates to a swim fin for use by a swimmer. The fin comprises a foot pocket adapted to receive a foot of the swimmer, a blade extending from the foot pocket, and a biasing system configured to allow the blade to bend within a narrow range of angles of attack under a wide range of loads.
The present invention also relates to a swim fin for use by a swimmer. The fin comprises a foot pocket adapted to receive a foot of the swimmer, a blade extending from the foot pocket, a biasing system configured to control the angle of attack of the blade. The biasing system comprises one or more biasing members such as a sinusoidal shaped rib.
The present invention further relates to a swim fin for use by a swimmer. The fin comprises a foot pocket adapted to receive a foot of the swimmer, a blade extending from the foot pocket, and means for controlling flexing of the blade.
The present invention further relates to a method of providing thrust from a kick by a swimmer. The method comprises providing a swim fin comprising a foot pocket, a blade, and one or more non-linear ribs that extend generally perpendicular to the blade. The method also comprises bending the blade relative to the foot pocket about an axis and controlling the bending of the blade by providing varying resistance by the non-linear ribs.
The present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. Other ways in which the objects and features of the disclosed embodiments are accomplished will be described in the following specification or will become apparent to those skilled in the art after they have read this specification. Such other ways are deemed to fall within the scope of the disclosed embodiments if they fall within the scope of the claims which follow.